There isn't much that can be said of Misery that hasn't already been said. It's a great movie-possibly the greatest adaptation of a Stephen King horror story- let down with a typical "how do I finish this thing?!" Stephen King ending, followed by an even stupider shock ending.
That's not to say it's perfect outside of the ending. I was really quite surprised by how, well, cheap it looks considering the year it was made and the fact that it largely takes place in a single room. I just don't know why it doesn't look good, but compare it with The Dead Zone or The Shining and it comes out looking like a high-budget made-for-TV movie.
The exposition can also get out of control. I don't think you really need to know anything about Annie's past... in fact it would have worked even better if you knew absolutely nothing about her other than she's crazy. Elaborate backgrounds work better in novels; in movies you should cut that stuff out. Put it on the movie poster or the back of the box if you really need to.
Having said that, none of this really detracts from the movie. The performances are great, and I really like the slow burn reveal of Annie's madness. The infamous "hobbling" scene still packs a punch, mostly because the movie up until that point has been so restrained that the sudden and graphic violence is a definite shock to the senses.
It's also got a really dark sense of humor that is subtle enough that you'd have to pay attention to notice it. I don't mean stupid stuff like the Farewell to Arms thing in Evil Dead 2. Classy stuff, like a big old pig. Or how Paul saves up all his painkillers so he can pour them into Annie's drink, but then she clumsily spills the glass and so he has to sit through a romantic dinner with her for nothing. Stuff like that.
Watch it, at least so you can see the pig!